Network path computation method, apparatus, and system

ABSTRACT

Embodiments of the present invention provide a network path computation method, apparatus and system, where the method includes: sending, by a first node, a path computation request to a first path computation element PCE, where the path computation request includes a resource sharing object, and a head node and a last node of a first label switched path LSP; and receiving, by the first node, a path computation result that is returned by the first PCE and that is obtained by means of computation according to the resource sharing object, and establishing a second path from the head node to the last node according to the path computation result. According to the network path computation method, apparatus, and system provided in the embodiments of the present invention, link resource utilization can be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2014/072049, filed on Feb. 13, 2014, which is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to network technologies, and inparticular, to a network path computation method, apparatus, and system.

BACKGROUND

In a network technology, a path computation element (PCE for short) is acentralized path computation element, which is mainly used to implementcomplex path computation. The PCE generally has network resourceinformation, including a topology, a node, and a current resource usagestatus. A main procedure of path computation is returning, after arequest from a path computation client (PCC for short) is received, pathinformation to the PCC by using a routing algorithm and with referenceto available resources of a current network. To enrich a dynamiccapability of the PCE, the IETF standardization organization furtherextends a function of the PCE, so that the PCE can acquire a labelswitched path (LSP for short). A PCE of this type is referred to as astateful PCE. In addition, an LSP Delegation function is also definedfor the PCE, that is, after the PCC grants a right of modifying an LSPto the PCE, the stateful PCE may modify the LSP when necessary, andinstruct a corresponding PCC to perform corresponding LSP update.

In a transport network, when a service encounters a fault, rerouting isan important means to recover the service. Rerouting indicates thatavailable route computation is performed again according to a resourcedistribution situation after the fault occurs, and service transmissionis recovered. In the prior art, after the fault occurs, a head nodesends a rerouting request to a PCE, requesting to compute a path,without releasing an original LSP connection. The PCE recomputes thepath according to resource information (including a faulty LSP). Whenthere is a path that meets a request, a computation result is returned;otherwise, a path computation failure is returned.

However, resource utilization of a rerouting method in the prior art isrelatively low. In some extreme scenarios, for example, when there arerelatively few available links in the network, and no available linksexcept an original LSP link can form a path from a head node to a lastnode, a path computation failure is also caused, and a service cannot berecovered.

SUMMARY

Embodiments of the present invention provide a network path computationmethod, apparatus, and system, so as to improve link resourceutilization.

According to a first aspect, an embodiment of the present inventionprovides a network path computation method, including:

sending, by a first node, a path computation request to a first pathcomputation element (PCE), where the path computation request includes aresource sharing object, and a head node and a last node of a firstlabel switched path (LSP); and

receiving, by the first node, a path computation result that is returnedby the first PCE and that is obtained by means of computation accordingto the resource sharing object, and establishing a second path from thehead node to the last node according to the path computation result.

In a first possible implementation manner of the first aspect, beforethe sending, by a first node, a path computation request to a first pathcomputation element (PCE), the method further includes:

determining, by the first node, that at least one link in a first labelswitched path LSP between a current head node and a current last nodefails.

According to the first aspect or the first possible implementationmanner of the first aspect, in a second possible implementation manner,the resource sharing object includes an identifier of the first labelswitched path (LSP) or an identifier of a normal link in the first labelswitched path (LSP).

According to the second possible implementation manner of the firstaspect, in a third possible implementation manner, the resource sharingobject further includes a sharing principle.

According to the third possible implementation manner of the firstaspect, in a fourth possible implementation manner, the sharingprinciple includes either of the following: sharing as many links aspossible is preferred; and a performance parameter is optimal in a casein which link sharing is ensured, where the performance parameterincludes a delay, jitter, or a hop count.

According to any one of the first aspect and the first to the fourthpossible implementation manners of the first aspect, in a fifth possibleimplementation manner, the path computation request further includes aninclude route object (IRO).

According to the first possible implementation manner of the firstaspect, in a sixth possible implementation manner, the head node and thelast node belong to a first-layer network, the first LSP between thehead node and the last node includes at least one link that belongs to asecond-layer network, and a head node of the link of the second-layernetwork is a third node;

the second path further includes at least one link in the second-layernetwork; and

after the receiving, by the first node, a path computation result thatis returned by the first PCE and that is obtained by means ofcomputation according to the resource sharing object, and establishing asecond path from the head node to the last node according to the pathcomputation result, the method further includes:

marking, by the first node, the second path as a second LSP, andsending, to the third node, information indicating that the second pathis marked as the second LSP, so that the third node sends a reportmessage to a second PCE in the second-layer network after marking thelink of the second-layer network as a third LSP, where the reportmessage includes a mapping relationship indicating that the third LSPand the second LSP serve a same service.

According to a second aspect, an embodiment of the present inventionprovides a network path computation method, including:

receiving, by a first path computation element (PCE), a path computationrequest sent by a first node, where the path computation requestincludes a resource sharing object, and a head node and a last node of afirst label switched path (LSP);

computing, by the first PCE, a second path from the head node to thelast node according to the resource sharing object; and

sending, by the first PCE, the second path to the first node, so thatthe first node establishes the second path from the head node to thelast node according to a path computation result.

In a first possible implementation manner of the second aspect, theresource sharing object includes an identifier of the first labelswitched path (LSP) or an identifier of a normal link in the first labelswitched path (LSP).

According to the first possible implementation manner of the secondaspect, in a second possible implementation manner, the resource sharingobject further includes a sharing principle.

According to the second possible implementation manner of the secondaspect, in a third possible implementation manner, the sharing principleincludes either of the following: sharing as many links as possible ispreferred; and a performance parameter is optimal in a case in whichlink sharing is ensured, where the performance parameter includes adelay, jitter, or a hop count.

According to any one of the first aspect and the first to the thirdpossible implementation manners of the second aspect, in a fourthpossible implementation manner, the path computation request furtherincludes an include route object (IRO).

In a fifth possible implementation manner of the second aspect, thecomputing, by the first PCE, a second path according to the resourcesharing object includes:

determining, by the first PCE, that a link resource of a first-layernetwork in which the first node and a second node are located isinsufficient to establish the second path; and

sending, by the first PCE to a second PCE in a second-layer network, arequest for establishing a third path, where the request includes theresource sharing object, the third path is used to form the second path,and the third path includes at least one link of the second-layernetwork.

According to a third aspect, an embodiment of the present inventionprovides a network path computation method, including:

receiving, by a second path computation element (PCE) in a second-layernetwork, a request for establishing a third path that is sent by a firstPCE in a first-layer network, where the request includes a resourcesharing object, and a head node and a last node in the second-layernetwork, the third path is used to form a second path, the third pathincludes at least one link of the second-layer network, and the secondpath further includes at least one link of the first-layer network; and

determining, by the second PCE, a shared target according to theresource sharing object and a mapping relationship between a linkresource of the second-layer network and a link resource of thefirst-layer network, and determining the third path according to theshared target.

In a first possible implementation manner of the third aspect, beforethe determining, by the second PCE, a shared target according to theresource sharing object and a mapping relationship between a linkresource of the first-layer network and a link resource of thesecond-layer network, the method further includes:

receiving, by the second PCE, a request for establishing a fourth paththat is sent by the first PCE, where the fourth path is used to form afirst path, the fourth path includes at least one link of thesecond-layer network, a head node of the second-layer network in thefourth path is a third node, and the first path further includes atleast one link of the first-layer network;

determining, by the second PCE, the fourth path according to therequest, and returning, to the first PCE, a message indicating that thefourth path is successfully computed;

establishing, by the second PCE, the fourth path, where the fourth pathis marked as a fourth LSP;

receiving, by the second PCE, a report message sent by the third node,where the report message includes information indicating that the firstpath is marked as a first LSP; and

establishing, by the second PCE, a mapping relationship indicating thatthe fourth LSP and the first LSP serve a same service, or receiving, bythe second PCE, a mapping relationship that is sent by the third nodeand that indicates that the fourth LSP and the first LSP correspondingto the first path serve a same service.

According to the third aspect or the first possible implementationmanner of the third aspect, in a second possible implementation manner,the mapping relationship between the link resource of the first-layernetwork and the link resource of the second-layer network is stored inan LSP database of the second-layer network.

According to a fourth aspect, an embodiment of the present inventionprovides a network path computation apparatus, including:

a sending module, configured to send a path computation request to afirst path computation element (PCE), where the path computation requestincludes a resource sharing object, and a head node and a last node of afirst label switched path (LSP); and

a receiving module, configured to receive a path computation result thatis returned by the first PCE and that is obtained by means ofcomputation according to the resource sharing object, and establish asecond path from the head node to the last node according to the pathcomputation result.

In a first possible implementation manner of the fourth aspect, theapparatus further includes:

a processing module, configured to determine, before the sending modulesends a path computation request to a path computation element (PCE),that at least one link in a first label switched path (LSP) between acurrent head node and a current last node fails.

According to the fourth aspect or the first possible implementationmanner of the fourth aspect, in a second possible implementation manner,the resource sharing object includes an identifier of the first labelswitched path (LSP) or an identifier of a normal link in the first labelswitched path (LSP).

According to the second possible implementation manner of the fourthaspect, in a third possible implementation manner, the resource sharingobject further includes a sharing principle.

According to the third possible implementation manner of the fourthaspect, in a fourth possible implementation manner, the sharingprinciple includes either of the following: sharing as many links aspossible is preferred; and a performance parameter is optimal in a casein which link sharing is ensured, where the performance parameterincludes a delay, jitter, or a hop count.

According to any one of the fourth aspect and the first to the fourthpossible implementation manners of the fourth aspect, in a fifthpossible implementation manner, the path computation request furtherincludes an include route object IRO.

According to the first possible implementation manner of the fourthaspect, in a sixth possible implementation manner, the head node and thelast node belong to a first-layer network, the first LSP between thehead node and the last node includes at least one link that belongs to asecond-layer network, and a head node of the link of the second-layernetwork is a third node;

the second path further includes at least one link in the second-layernetwork; and

the processing module is further configured to mark the second path as asecond LSP, and the sending module is further configured to send, to thethird node, information indicating that the second path is marked as thesecond LSP, so that the third node sends a report message to a secondPCE in the second-layer network after marking the link of thesecond-layer network as a third LSP, where the report message includes amapping relationship indicating that the third LSP and the second LSPserve a same service.

According to a fifth aspect, an embodiment of the present inventionprovides a network path computation apparatus, including:

a receiving module, configured to receive a path computation requestsent by a first node, where the path computation request includes aresource sharing object, and a head node and a last node of a firstlabel switched path (LSP);

a processing module, configured to compute a second path from the headnode to the last node according to the resource sharing object; and

a sending module, configured to send the second path to the first node,so that the first node establishes the second path from the head node tothe last node according to a path computation result.

In a first possible implementation manner of the fifth aspect, theresource sharing object includes an identifier of the first labelswitched path (LSP) or an identifier of a normal link in the first labelswitched path (LSP).

According to the first possible implementation manner of the fifthaspect, in a second possible implementation manner, the resource sharingobject further includes a sharing principle.

According to the second possible implementation manner of the fifthaspect, in a third possible implementation manner, the sharing principleincludes either of the following: sharing as many links as possible ispreferred; and a performance parameter is optimal in a case in whichlink sharing is ensured, where the performance parameter includes adelay, jitter, or a hop count.

According to any one of the fifth aspect and the first to the thirdpossible implementation manners of the fifth aspect, in a fourthpossible implementation manner, the path computation request furtherincludes an include route object (IRO).

In a fifth possible implementation manner of the fifth aspect, theprocessing module is specifically configured to:

determine that a link resource of a first-layer network in which thefirst node and a second node are located is insufficient to establishthe second path; and

send, to a second PCE in a second-layer network, a request forestablishing a third path, where the request includes the resourcesharing object, the third path is used to form the second path, and thethird path includes at least one link of the second-layer network.

According to a sixth aspect, an embodiment of the present inventionprovides a network path computation apparatus, including:

a receiving module, configured to receive a request for establishing athird path that is sent by a first PCE in a first-layer network, wherethe request includes a resource sharing object, and a head node and alast node in a second-layer network, the third path is used to form asecond path, the third path includes at least one link of thesecond-layer network, and the second path further includes at least onelink of the first-layer network; and

a processing module, configured to determine a shared target accordingto the resource sharing object and a mapping relationship between a linkresource of the second-layer network and a link resource of thefirst-layer network, and determine the third path according to theshared target.

In a first possible implementation manner of the sixth aspect,

the receiving module is further configured to receive, before theprocessing module determines the shared target according to the resourcesharing object and the mapping relationship between the link resource ofthe first-layer network and the link resource of the second-layernetwork, a request for establishing a fourth path that is sent by thefirst PCE, where the fourth path is used to form a first path, thefourth path includes at least one link of the second-layer network, ahead node of the second-layer network in the fourth path is a thirdnode, and the first path further includes at least one link of thefirst-layer network;

the processing module is further configured to determine the fourth pathaccording to the request, and return, to the first PCE, a messageindicating that the fourth path is successfully computed;

the processing module is further configured to establish the fourthpath, where the fourth path is marked as a fourth LSP;

the receiving module is further configured to receive a report messagesent by the third node, where the report message includes informationindicating that the first path is marked as a first LSP; and

the processing module is further configured to establish a mappingrelationship indicating that the fourth LSP and the first LSP serve asame service, or the receiving module is further configured to receive amapping relationship that is sent by the third node and that indicatesthat the fourth LSP and the first LSP corresponding to the first pathserve a same service.

According to the sixth aspect or the first possible implementationmanner of the sixth aspect, in a second possible implementation manner,the mapping relationship between the link resource of the first-layernetwork and the link resource of the second-layer network is stored inan LSP database of the second-layer network.

According to a seventh aspect, an embodiment of the present inventionprovides a network path computation system, including: a pathcomputation client (PCC) in which the network path computation apparatusin the embodiment shown in FIG. 6 or FIG. 7 is disposed or the firstnode in the embodiment shown in FIG. 10, and a path computation element(PCE) in which the network path computation apparatus described in theembodiment shown in FIG. 8 is disposed or the first PCE in theembodiment shown in FIG. 11.

According to an eighth aspect, an embodiment of the present inventionprovides a network path computation system, including: a pathcomputation client (PCC) in which the network path computation apparatusin the embodiment shown in FIG. 6 or FIG. 7 is disposed or the firstnode in the embodiment shown in FIG. 10, a first path computationelement (PCE) that is located in a first-layer network and in which thenetwork path computation apparatus in the embodiment shown in FIG. 8 isdisposed or the first PCE in the embodiment shown in FIG. 11, and asecond PCE that is located in a second-layer network and in which thenetwork path computation apparatus in the embodiment shown in FIG. 9 isdisposed or the second PCE in the embodiment shown in FIG. 12.

According to the network path computation method, apparatus, and systemprovided in the embodiments of the present invention, a resource sharingobject is added to a path computation request sent by a first node to aPCE, so as to declare an object that needs to be shared; and the PCEcomputes a path according to the resource sharing object, that is, whencomputing the path, the PCE may reuse an original link resource or alink resource in a fault-free section in a faulty path. In this way,link resource utilization can be improved, and in a scenario of fewavailable link resources in a network, a path computation success ratecan be improved.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly describes the accompanyingdrawings required for describing the embodiments. Apparently, theaccompanying drawings in the following description show some embodimentsof the present invention, and persons of ordinary skill in the art maystill derive other drawings from these accompanying drawings withoutcreative efforts.

FIG. 1 is a signaling flowchart of Embodiment 1 of a path computationmethod according to the present invention;

FIG. 2 is a schematic structural diagram of a network to which a methodembodiment shown in FIG. 1 is applied;

FIG. 3A and FIG. 3B are a signaling flowchart of Embodiment 2 of a pathcomputation method according to the present invention;

FIG. 4 is a schematic structural diagram of a network to which a methodembodiment shown in FIG. 3A and FIG. 3B is applied;

FIG. 5A and FIG. 5B are a signaling flowchart of Embodiment 3 of a pathcomputation method according to the present invention;

FIG. 6 is a schematic structural diagram of Embodiment 1 of a networkpath computation apparatus according to the present invention;

FIG. 7 is a schematic structural diagram of Embodiment 2 of a networkpath computation apparatus according to the present invention;

FIG. 8 is a schematic structural diagram of Embodiment 3 of a networkpath computation apparatus according to the present invention;

FIG. 9 is a schematic structural diagram of Embodiment 4 of a networkpath computation apparatus according to the present invention;

FIG. 10 is a schematic structural diagram of an embodiment of a firstnode according to the present invention;

FIG. 11 is a schematic structural diagram of Embodiment 1 of a PCEaccording to the present invention;

FIG. 12 is a schematic structural diagram of Embodiment 2 of a PCEaccording to the present invention;

FIG. 13 is a schematic structural diagram of Embodiment 1 of a networkpath computation system according to the present invention; and

FIG. 14 is a schematic structural diagram of Embodiment 2 of a networkpath computation system according to the present invention.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of theembodiments of the present invention clearer, the following clearlydescribes the technical solutions in the embodiments of the presentinvention with reference to the accompanying drawings in the embodimentsof the present invention. Apparently, the described embodiments are somebut not all of the embodiments of the present invention. All otherembodiments obtained by persons of ordinary skill in the art based onthe embodiments of the present invention without creative efforts shallfall within the protection scope of the present invention.

The present invention provides a path computation method that supports asharing policy, which allows an existing link or LSP to be shared in apath computation process. The sharing policy is a policy of reroutingafter a service encounters a fault, and the policy allows reusing a partof resources of the service currently affected by the fault. Forexample, one LSP includes four nodes A, B, C, D and links between thenodes. When the link between C and D fails, the LSP fails, but A-B andB-C are fault-free sections, and the like. In this case, the sharingpolicy allows reusing the A-B and B-C links in the LSP.

In addition, the method in this embodiment of the present invention cansupport interaction between multiple PCEs, thereby implementing resourcesharing when a cross-layer and cross-domain path is computed.

FIG. 1 is a signaling flowchart of Embodiment 1 of a path computationmethod according to the present invention. This embodiment is applicableto a single-layer network scenario. As shown in FIG. 1, the method inthis embodiment is completed by a PCE and a first node by means ofinteraction. The method in this embodiment may include the followingsteps:

Step 101: A first node sends a path computation request to a PCE, wherethe path computation request includes a resource sharing object, and ahead node and a last node of a first label switched path LSP.

The first node may be a head node, or may be another node. FIG. 1 showsonly a case in which the first node is a head node. In this case, thefirst node serves as a path computation client (PCC for short).

In a specific implementation process, the PCC initiates the pathcomputation request by sending a PCReq message to the PCE, where the PCCis not limited to any device, and may be a node, a controller, oranother PCE.

The path computation request may be a PCReq command.

Preferably, the method in this embodiment may be applied to a scenarioof rerouting after an original link between the head node and the lastnode fails, for example, a scenario in which a first path from the headnode to the last node fails. The foregoing step 101, that is, a processin which the first node requests rerouting from the PCE, differs fromthe prior art in that the path computation request includes the resourcesharing object (RSO for short), and the resource sharing object mayinclude an identifier of the first label switched path LSP or anidentifier of a normal link in the first label switched path LSP.

Further, the resource sharing object may further include a sharingprinciple, and the sharing principle may include either of thefollowing: sharing as many links as possible is preferred; some specificperformance parameters (parameters such as a delay, jitter, and a hopcount) are optimal in a case in which link sharing is ensured. Inaddition, the sharing policy may coexist with other policies (such asbandwidth throttling and delay limitation).

Step 102: The PCE computes a second path from the head node to the lastnode according to the resource sharing object.

Specifically, after receiving the path computation request that includesthe RSO, the PCE may preferentially consider a choice from routes sharedwith a specified object, and return a computation result; when thesharing policy cannot be met, but there is still an available resourcebetween the head node and the last node (a source node and a sink node),return a computation result of non-sharing; and when a requirement for aresource between the source node and the sink node cannot be metregardless of whether the sharing policy is met, return a resultindicating a path computation failure.

Step 103: The PCE sends the second path to the first node.

Step 104: The first node establishes the second path from the head nodeto the last node according to the path computation result.

In specific implementation, a method for establishing the second path isnot necessarily completed by the first node, and another manner may beused. For example, the method may also be as follows: The PCE sends apath establishment instruction to each node in the second path, and eachnode establishes a respective connection after receiving theinstruction.

It should be noted that the PCE in this embodiment may be a PCE in asingle-layer network, or may be a PCE in a network at a specific layerin a multi-layer network scenario, for example, a first PCE or a secondPCE described in a subsequent embodiment.

The following describes the method in this embodiment in detail withreference to a specific network. FIG. 2 is a schematic structuraldiagram of a network to which a method embodiment shown in FIG. 1 isapplied. As shown in FIG. 2, the network includes at least one PCE, andS, I1, I2, and D are nodes in the network. When a service from the nodeS to the node D needs to be established, the head node S initiates apath computation request to the PCE to request to establish the servicefrom the node S to the node D, and the PCE computes a path and returns aresult indicating that a working path of the service is S-I1-I2-D, andan LSP of the path is marked as a first LSP. However, when a faultoccurs in an I1-I2 section, the first node S senses the fault, and theninitiates a rerouting request to the PCE. If a path computation methodin the prior art is used, because resource sharing is not supported inthe prior art, and in this case, available link resources are I1-I3 andI3-D, which are insufficient to form the service from the node S to thenode D, the PCE returns, to the first node S, a result indicating a pathcomputation failure.

However, according to the method in this embodiment, because the pathcomputation request in step 101 includes a second node and a resourcesharing object, in the network shown in FIG. 2, the resource sharingobject may be specified as a first LSP, and sharing a resource with thefirst LSP is required. Specifically, the resource sharing object mayinclude an identifier of a resource that needs to be shared, that is, afirst LSP1, which may also be expressed in another form, provided thatthe shared resource is specified. In addition to specifying the sharedresource as the first LSP, the RSO may further specify a sharingprinciple. The sharing principle includes but is not limited to: it isrequired that sharing as many links as possible be preferred; andanother performance parameter is optimal in a case in which link sharingis ensured, where the performance parameter includes but is not limitedto a delay, jitter, and a hop count. If the sharing policy is thatsharing as many links as possible is preferred, an available path havinga relatively high degree of sharing with a specified object ispreferentially selected. For example, there are two available paths: oneshares three hops with an original path, and the other shares two hops;in this case, the path sharing three hops is preferentially selected.

In step 102 in which the PCE computes a second path from the head nodeto the last node according to the resource sharing object, a fault-freesection in the first LSP may be reused, that is, a section S-I1 and asection I2-D may be reused. With reference to a current resource usagestatus, the PCE may also query an LSP database to obtain a preferredpath S-I1-I3-D. This path has resource sharing with the first LSP in thesection S-I1. After this path is established, a corresponding LSP may bemarked as a second LSP.

Similarly, for the network shown in FIG. 2, if a service needs to beswitched back after a fault in I1-I2 is rectified, the switchback mayalso be implemented by using the method in the embodiment shown inFIG. 1. In specific implementation, after the fault occurs in I1-I2 andrerouting is complete, the node S may periodically send a pathcomputation request (PCReq instruction) to the PCE, where the pathcomputation request may include an include route object (IRO for short),and the IRO refers to an object that is “necessarily included”. Thisembodiment is applied to the network shown in FIG. 2. The IRO may bespecified as a first LSP, representing that an LSP1 is an include pathfor recovery; the RSO may be specified as an LSP2, indicating thatsharing with the LSP2 is allowed. In this way, before the fault in I1-I2disappears, the PCE fails to compute a path, and returns a pathcomputation failure message to the node S; when the fault in I1-I2disappears, the PCE returns a path computation success to the node S.

In this embodiment, a resource sharing object is added to a pathcomputation request sent by a first node to a PCE, so as to declare anobject that needs to be shared; and the PCE computes a path according tothe resource sharing object, that is, when computing the path, the PCEmay reuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

It should be noted that in specific implementation, when the first nodedetermines that a link resource does not need to be shared, the RSO inthe path computation request may be omitted by default.

The path computation method in the present invention may also be appliedto a multi-layer network scenario. A multi-layer network is anapplication of a transport network nowadays. Typical scenarios includean Internet Protocol (IP for short) layer, an optical layer, and thelike. In the multi-layer network scenario, the IP layer and the opticallayer each have a PCE that is responsible for path computation. Itshould be noted that because a service path in the foregoing embodimentrelates only to a single-layer network, if the service path correspondsto the multi-layer network, the PCE in the foregoing embodiment maycorrespond to a first PCE in a first-layer network, or may correspond toa second PCE in a second-layer network, or may correspond to a PCE atanother layer, which is not limited in the present invention.

In the multi-layer network scenario, when it is found that resources areinsufficient to establish a service, the IP layer may request pathcomputation from a PCE at the optical layer, and use resources of theoptical layer to complete establishment of the service. In thisscenario, a PCE at the IP layer and a PCE at the optical layer need toperform cooperative computation. In this case, after two PCEs innetworks at two layers separately complete path computation, and afterhead nodes in the networks at two layers and a corresponding node in anetwork on another side separately establish a path, a PCE in thesecond-layer network (that is, a second PCE) or a head node of thesecond-layer network needs to establish a mapping relationship betweenthe two paths, to declare that the two paths serve a same service, sothat a sharing policy can be used according to the mapping relationshipin a subsequent cross-layer path computation process.

Specifically, the head node and the last node belong to a first-layernetwork, the first LSP between the head node and the last node includesat least one link that belongs to a second-layer network, and a headnode of the link of the second-layer network is a third node.

The second path after rerouting further includes the at least one linkof the second-layer network.

After the foregoing step 104, the method may further include:

marking, by the first node, the second path as a second LSP, andsending, to the third node, information indicating that the second pathis marked as the second LSP, so that the third node sends a reportmessage to a second PCE in the second-layer network after marking thelink of the second-layer network as a third LSP, where the reportmessage includes a mapping relationship indicating that the third LSPand the second LSP serve a same service.

In this way, in a subsequent rerouting process, after the second PCEreceives a path computation request that includes an RSO, if the RSO isthe second LSP, the second PCE may determine a shared target in thesecond-layer network as the third LSP according to the mappingrelationship.

FIG. 3A and FIG. 3B are a signaling flowchart of Embodiment 2 of a pathcomputation method according to the present invention. In thisembodiment, both a head node and a last node are located in afirst-layer network; however, when computing a path between the headnode and the last node, a first PCE in the first-layer network needs touse a link that belongs to a second-layer network. The method in thisembodiment is completed, by means of interaction, by the first PCE inthe first-layer network, the head node located in the first-layernetwork, a second node and a third node that are interaction nodes ofthe first-layer network and the second-layer network, and a second PCEin the second-layer network, where the second node is located in thefirst-layer network and the third node is located in the second-layernetwork. This embodiment describes a process in which the head node andthe last node establish a cross-layer path for the first time, andestablish a mapping relationship between link resources of networks attwo layers. As shown in FIG. 3A and FIG. 3B, the method in thisembodiment may include the following steps:

Step 301: A first node located in a first-layer network sends a pathcomputation request to a first PCE, where the path computation requestincludes a head node and a last node.

The first node may be the head node, or may be another node or anotherPCC. FIG. 3A and FIG. 3B or this embodiment shows only a case in whichthe first node is the head node.

Step 302: The first PCE computes a first path from the head node to thelast node according to the path computation request, where when aresource of the first-layer network cannot meet a requirement, the firstpath includes at least one link of the first-layer network and at leastone link of a second-layer network.

In specific implementation, the first PCE may compute a head node and alast node of the at least one link of the second-layer network, and anode that is in the first-layer network and that is connected to thehead node and the last node of the link of the second-layer network, butcannot acquire a path between the head node and the last node of thelink of the second-layer network. For ease of description, in thisembodiment, the path is referred to as a fourth path.

Step 303: The first PCE sends, to a second PCE in the second-layernetwork, a request for establishing a fourth path, where the fourth pathincludes at least one link of the second-layer network.

Step 304: The second PCE determines the fourth path according to therequest, and returns, to the first PCE, a message indicating that thefourth path is successfully computed.

Step 305: The first PCE sends a path establishment command to the firstnode according to the first path, where the first path includes the headnode, the last node, and at least two nodes that belong to thesecond-layer network.

A node that is of the at least two nodes of the second-layer network andthat is connected to a node in the first-layer network is a third node,and the third node may be referred to as a head node in the second-layernetwork.

Step 306: The first node establishes a path from the head node to thelast node according to the path establishment command, and marks thepath as a first LSP.

The first LSP is the first path. In specific implementation, a methodfor establishing the first path is not necessarily completed by thefirst node, and another manner may be used. For example, the method mayalso be as follows: The first PCE sends a path establishment instructionto each node that is in the first path and that belongs to thefirst-layer network, and each node establishes a respective connectionafter receiving the instruction.

In addition, in specific implementation, the first path may also bemarked as the first LSP by the first PCE or another node. In addition,after step 306, a first-layer network node (the node may be the firstnode, or may be another node) connected to the third node needs to send,to the third node, a message indicating that the first path is marked asthe first LSP.

Step 307: The third node establishes, in the path, a path that includesthe at least two nodes belonging to the second-layer network, and marksthe path as a fourth LSP.

The fourth LSP is a fourth path. In specific implementation, a methodfor establishing the fourth path is not necessarily completed by thethird node, and another manner may be used. For example, the method mayalso be as follows: The second PCE sends a path establishmentinstruction to each node that is in the fourth path and that belongs tothe second-layer network, and each node establishes a respectiveconnection after receiving the instruction.

Step 308: The third node sends a report message to the second PCE, wherethe report message includes a mapping relationship indicating that thefirst LSP and the fourth LSP serve a same service.

In specific implementation, in addition to using the method of step 308,the mapping relationship indicating that the first LSP and the fourthLSP serve the same service may also be established by the second PCE.

Specifically, the report message may be forwarded to the second PCE by anode in the first-layer network by using the third node.

The following describes this embodiment in detail with reference to aspecific cross-layer network. FIG. 4 is a schematic structural diagramof a network to which a method embodiment shown in FIG. 3A and FIG. 3Bis applied. In FIG. 4, a first-layer network is an IP layer, a first PCEis an IP-PCE, a second-layer network is an optical layer, and a secondPCE is an O-PCE. Path computation at the IP layer and the optical layeris respectively performed by the IP-PCE and the optical-PCE (O-PCE). Inaddition, two PCEs may transfer a path computation request and return aresult by using the PCEP. In this embodiment, a head node is a node S,and a last node is a node D. An example in which the head node Srequests the PCE at the IP layer to establish a path from the node S tothe node D is used to describe a cross-layer path computation process,and lays a basis for subsequent computation of a shared path.

Computation and establishment of a cross-layer path require thefollowing steps:

In step 301, the node S sends a path computation request to the firstPCE (IP-PCE), and the last node is set as D. A resource sharing objectmay not be specified in this step.

In step 302, the IP-PCE determines that IP1-IP5 in a first path from ahead node to a last node needs to be a link of an optical layer network.

In step 303, the IP-PCE requests an IP1-IP5 path from the O-PCE. In thiscase, the resource sharing object may also not be specified.

In step 304, the O-PCE determines, by means of computation, that anoptical layer path (a fourth path) corresponding to the IP1-IP5 path isO1-O2-O5, and notifies the IP-PCE of an optical layer path computationsuccess. The O1 is a head node of a path of a second-layer network, thatis, a third node. The IP1 is a node that is in a path of a first-layernetwork and that is connected to the head node of the path of thesecond-layer network.

In step 305, the IP-PCE delivers a path establishment command to thenode S, where a route is S-IP1-(O1-O5)-IP5-D, that is, the first path isS-IP1-(O1-O5)-IP5-D.

In step 306, the node S establishes the first path, and marks the firstpath as a first LSP.

In step 307, the IP1 instructs the third node O1 to establish an opticallayer link, that is, a fourth path, and marks the fourth path as afourth LSP.

In step 308, the IP1 forwards a report message (PCRpt) to the O-PCE byusing the O1, to declare a mapping relationship indicating that thefirst LSP (or an IP1-IP5 link) and the fourth LSP (or an O1-O2-O5 link)serve a same service. The mapping relationship may be stored in an LSPDatabase of the O-PCE, where the mapping relationship may be that thefirst LSP corresponds to the fourth LSP, or the (IP1-IP5) linkcorresponds to the fourth LSP. In specific implementation, when the IP1and the O1 are a same device, the foregoing relationship may be directlysent to the O-PCE by the O1; when the IP1 and the O1 are differentdevices, the foregoing relationship is sent to the O-PCE by the IP1 viathe O1.

So far, establishment of a cross-layer path is complete, and a mappingrelationship between link resources is also stored in the O-PCE.

According to the path establishment method in this embodiment, when apath is established, a mapping relationship between a link of afirst-layer network and a link of a second-layer network is saved, whichmay be used for subsequent sharing policy-based path computation. Aspecific method is described in detail in the following Embodiment 3 ofa path computation method.

FIG. 5A and FIG. 5B are a signaling flowchart of Embodiment 3 of a pathcomputation method according to the present invention. A method forrerouting according to a mapping relationship between link resources ina cross-layer network is described in this embodiment. This embodimentis applicable to a scenario in which a path needs to be re-establishedafter a fault occurs in a cross-layer path in a multi-layer network. Forexample, after the embodiment shown in FIG. 3A and FIG. 3B is complete,and after a fault occurs in a first path or a fourth path, the method inthis embodiment may be used to perform rerouting. As shown in FIG. 5Aand FIG. 5B, the method in this embodiment may include the followingsteps:

Step 501: A first node located in a first-layer network sends a pathcomputation request to a first PCE, where the path computation requestincludes a head node and a last node of a second path, and a resourcesharing object.

In this embodiment, step 501 is triggered when the head node senses afault of a first path between a current head node and a current lastnode. With reference to a network structure shown in FIG. 4, that is,S-IP1-(O1-O5)-IP5-D, for ease of description, it is assumed herein thatthe fault of the first path is specifically that an O2-O5 optical linkencounters a fault, after sensing the fault, a node S requests rerouting(an example of rerouting with “a same source node and a same sink node”is used in this embodiment for description; actually, the rerouting maybe rerouting with a same source node but a different sink node, with adifferent source node but a same sink node, or with a different sourcenode and a different sink node) from an IP-PCE, and computes a secondpath from the node S to a node D.

The first node may be the head node, or may be another node or anotherPCC. FIG. 5A and FIG. 5B show only a case in which the first node is thehead node.

Step 502: The first PCE computes the second path from the head node tothe last node according to the resource sharing object, where when aresource of the first-layer network cannot meet a requirement, thesecond path includes at least one link of the first-layer network and atleast one link of a second-layer network.

With reference to FIG. 4, the second path may beS-IP1-(O1-O5)-IP4-IP5-D, where O1-O5 is a link of the second-layernetwork, and a specific path of O1-O5 needs to be computed by a PCE atan optical layer.

Step 503: The first PCE sends, to the second PCE, a request forestablishing a third path, where the request includes the resourcesharing object, and a head node and a last node in the second-layernetwork, and the third path includes at least one link of thesecond-layer network.

With reference to FIG. 4 and Embodiment 2 of the path computation methodin the present invention, the resource sharing object may be a first LSP(or an IP1-IP5 link).

Step 504: The second PCE determines a shared target according to theresource sharing object and a mapping relationship between a linkresource of the first-layer network and a link resource of thesecond-layer network, determines the third path according to the sharedtarget, and then returns, to the first PCE, a message indicating thatthe third path is successfully computed.

In an example shown in FIG. 4, according to Embodiment 2 of theforegoing path computation method, the second PCE may determine that thefirst LSP or the IP1-IP5 link corresponds to a fourth LSP at an opticallayer or an O1-O2-O5 link at an optical layer; therefore, a fault-freeO1-O2 link may be shared, and the second PCE may determine that thethird path is O1-O2-O4-O5.

Step 505: The first PCE determines the second path from the head node tothe last node, and sends a path establishment command to the first node,where the second path includes the first node, the second node, and atleast two nodes that belong to the second-layer network.

A node that is a first node of the at least two nodes of thesecond-layer network and that is connected to a node in the first-layernetwork is a third node, and the third node is a head node of thesecond-layer network in the second path. For example, with reference toFIG. 4, interconnections between nodes of the first-layer network andthe second-layer network are a connection between IP1 and O1 and aconnection between IP5 and O5, and O1 is the head node of thesecond-layer network in the second path; therefore, the third node isO1.

In the example shown in FIG. 4, the second path may be:S-IP1-(O1-O5)-IP5-D.

Step 506: The first node establishes the second path from the head nodeto the last node according to the path establishment command, and marksthe second path as a second LSP.

In addition, in specific implementation, the second path may also bemarked as the second LSP by the first PCE or another node. In addition,after step 506, a first-layer network node (the node may be the firstnode, or may be another node) connected to the third node needs to send,to the third node, a message indicating that the first path is marked asthe first LSP.

Step 507: The third node establishes, in the second path, a third paththat includes the at least two nodes belonging to the second-layernetwork, and marks the third path as a third LSP.

In specific implementation, the third node may establish the third pathaccording to an instruction of the second PCE. The instruction may besent by the first PCE to the second PCE.

Alternatively, the third path may be marked as the third LSP by thesecond PCE or another node.

For the example shown in FIG. 4, the third path may be:IP1-O1-O2-O4-O5-IP5.

Step 508: The third node sends a report message to the second PCE, wherethe report message includes a mapping relationship indicating that thesecond LSP and the third LSP serve a same service.

In specific implementation, the mapping relationship indicating that thesecond LSP and the third LSP serve the same service may also beestablished by the second PCE.

According to the method in this embodiment, based on an existing mappingrelationship between a link of a first-layer network and a link of asecond-layer network, path computation with a sharing policy can beperformed in a cross-layer scenario.

FIG. 6 is a schematic structural diagram of Embodiment 1 of a networkpath computation apparatus according to the present invention. Thenetwork path computation apparatus in this embodiment may be disposed ona first node, or may be a first node itself. As shown in FIG. 6, anapparatus 600 in this embodiment may include: a sending module 601 and areceiving module 602.

The sending module 601 is configured to send a path computation requestto a first path computation element PCE, where the path computationrequest includes a resource sharing object, and a head node and a lastnode of a first label switched path LSP.

The receiving module 602 is configured to receive a path computationresult that is returned by the first PCE and that is obtained by meansof computation according to the resource sharing object, and establish asecond path from the head node to the last node according to the pathcomputation result.

Further, the resource sharing object includes an identifier of the firstlabel switched path LSP or an identifier of a normal link in the firstlabel switched path LSP.

Further, the resource sharing object further includes a sharingprinciple.

Further, the sharing principle includes either of the following: sharingas many links as possible is preferred; and a performance parameter isoptimal in a case in which link sharing is ensured, where theperformance parameter includes but is not limited to a delay, jitter, ora hop count.

The apparatus in this embodiment may be used to execute the technicalsolution that is executed by the corresponding first node in the methodembodiment shown in FIG. 1, and the implementation principles of thetechnical solutions are similar and are not described herein again.

The apparatus in this embodiment adds a resource sharing object to apath computation request sent to a PCE, so as to declare an object thatneeds to be shared; and the PCE computes a path according to theresource sharing object, that is, when computing the path, the PCE mayreuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

The apparatus in the foregoing embodiment may be applied to a scenarioin which a first path from a head node to a last node fails. Because asharing policy is used, for example, a path computation request requiresthat a fault-free link in the first path be shared, so that duringcomputation, the PCE can preferentially consider a choice from routesshared with a specified object, and return a computation result; whenthe sharing policy cannot be met, but there is still an availableresource between the head node and the last node (a source node and asink node), return a computation result of non-sharing; and when arequirement for a resource between the source node and the sink nodecannot be met regardless of whether the sharing policy is met, return aresult indicating a path computation failure.

Further, the path computation request may further include an includeroute object IRO. The IRO refers to an object that is “necessarilyincluded”. The solution may be applied to a scenario of switchback to anoriginal link after rerouting. For example, the network path computationapparatus in this embodiment may periodically send a path computationrequest to a PCE, and set the IRO as a link of the first path. In thisway, the PCE can obtain a result indicating a path computation successonly when a fault in the first path is rectified.

FIG. 7 is a schematic structural diagram of Embodiment 2 of a networkpath computation apparatus according to the present invention. Thenetwork path computation apparatus in this embodiment may be disposed ona first node, or may be a first node itself. As shown in FIG. 7, on thebasis of the embodiment shown in FIG. 6, an apparatus 700 in thisembodiment may further include a processing module 603, where theprocessing module 603 is configured to determine, before a first nodesends a path computation request to a path computation element PCE, thatat least one link in a first label switched path LSP between a currenthead node and a current last node fails.

Further, the apparatus in the embodiment shown in FIG. 6 or FIG. 7 mayalso be applied to a multi-layer network scenario. A multi-layer networkis an application of a transport network nowadays. Typical scenariosinclude an IP layer, an optical layer, and the like. In the multi-layernetwork scenario, the IP layer and the optical layer each have a PCEthat is responsible for path computation.

When the apparatus is applied to the multi-layer network scenario,specifically, the head node and the last node belong to a first-layernetwork, the first LSP between the head node and the last node includesat least one link that belongs to a second-layer network, and a headnode of the link of the second-layer network is a third node.

The second path further includes the at least one link in thesecond-layer network.

The processing module 603 is further configured to mark the third pathas a third LSP, and the sending module is further configured to send, tothe third node, information indicating that the second path is marked asa second LSP, so that the third node sends a report message to a secondPCE in the second-layer network after marking the link of thesecond-layer network as the third LSP, where the report message includesa mapping relationship indicating that the third LSP and the second LSPserve a same service.

In this way, based on the mapping relationship indicating that the thirdLSP and the second LSP serve the same service, in a subsequentcross-layer path computation process, if a specified shared object isthe second LSP, a PCE in a network on another side may determine ashared target in the network at this layer according to the mappingrelationship, so as to support a sharing policy when a cross-layer pathis computed.

The apparatus in this embodiment may be used to execute the technicalsolution that is executed by the corresponding first node in the methodembodiment shown in FIG. 1, FIG. 4, or FIG. 5A and FIG. 5B, and theimplementation principles and technical effects of the technicalsolutions are similar and are not described herein again.

FIG. 8 is a schematic structural diagram of Embodiment 3 of a networkpath computation apparatus according to the present invention. Theapparatus in this embodiment may be disposed on a PCE, or may be a PCEitself. The PCE may serve as a PCE in a single-layer network, or mayserve as a PCE in a first-layer network of a multi-layer network (whichis referred to as a first PCE). As shown in FIG. 8, an apparatus 800 inthis embodiment may include: a receiving module 801, a processing module802, and a sending module 803.

The receiving module 801 is configured to receive a path computationrequest sent by a first node, where the path computation requestincludes a resource sharing object, and a head node and a last node of afirst label switched path LSP.

The processing module 802 is configured to compute a second path fromthe head node to the last node according to the resource sharing object.

The sending module 803 is configured to send the second path to thefirst node, so that the first node establishes the second path from thehead node to the last node according to the path computation result.

Further, the resource sharing object includes an identifier of the firstlabel switched path LSP or an identifier of a normal link in the firstlabel switched path LSP.

Further, the resource sharing object further includes a sharingprinciple.

Further, the sharing principle includes either of the following: sharingas many links as possible is preferred; and a performance parameter isoptimal in a case in which link sharing is ensured, where theperformance parameter includes but is not limited to a delay, jitter, ora hop count.

Further, the path computation request further includes an include routeobject IRO.

Further, when the apparatus is applied to a multi-layer network, theprocessing module 802 is specifically configured to:

determine that a link resource of a first-layer network in which thefirst node and the second node are located is insufficient to establishthe second path; and

send, to a second PCE in a second-layer network, a request forestablishing a third path, where the request includes the resourcesharing object, the third path is used to form the second path, and thethird path includes at least one link of the second-layer network.

The apparatus in this embodiment may be used to execute the technicalsolution that is executed by the corresponding PCE in the methodembodiment shown in FIG. 1, or the technical solution that is executedby the corresponding first PCE in the method embodiment shown in FIG. 3Aand FIG. 3B, or FIG. 5A and FIG. 5B, and the implementation principlesof the technical solutions are similar and are not described hereinagain.

The apparatus in this embodiment adds a resource sharing object to apath computation request sent to a PCE, so as to declare an object thatneeds to be shared; and the PCE computes a path according to theresource sharing object, that is, when computing the path, the PCE mayreuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

FIG. 9 is a schematic structural diagram of Embodiment 4 of a networkpath computation apparatus according to the present invention. Theapparatus in this embodiment may be disposed on a PCE, or may be a PCEitself. The PCE may serve as a PCE in a single-layer network, or mayserve as a PCE in a second-layer network of a multi-layer network (whichis referred to as a second PCE). As shown in FIG. 9, an apparatus 900 inthis embodiment may include: a receiving module 901 and a processingmodule 902.

The receiving module 901 is configured to receive a request forestablishing a third path that is sent by a first PCE in a first-layernetwork, where the request includes the resource sharing object, and ahead node and a last node in a second-layer network, the third path isused to form a second path, the third path includes at least one link ofthe second-layer network, and the second path further includes at leastone link of the first-layer network.

The processing module 902 is configured to determine a shared targetaccording to the resource sharing object and a mapping relationshipbetween a link resource of the second-layer network and a link resourceof the first-layer network, and determine the third path according tothe shared target.

The apparatus in this embodiment may be used to execute the technicalsolution that is executed by the corresponding second PCE in the methodembodiment shown in FIG. 3A and FIG. 3B, and the implementationprinciples and technical effects of the technical solutions are similarand are not described herein again.

Further, in another scenario, for example, when a cross-layer path isestablished for the first time, the receiving module 901 is furtherconfigured to receive, before the second PCE determines the sharedtarget according to the resource sharing object and the mappingrelationship between the link resource of the first-layer network andthe link resource of the second-layer network, a request forestablishing a fourth path that is sent by the first PCE, where thefourth path is used to form a first path, the fourth path includes atleast one link of the second-layer network, a head node of thesecond-layer network in the fourth path is a third node, and the firstpath further includes at least one link of the first-layer network.

The processing module 902 is further configured to determine the fourthpath according to the request, and return, to the first PCE, a messageindicating that the fourth path is successfully computed.

The processing module 902 is further configured to establish the fourthpath, where the fourth path is marked as a fourth LSP.

The receiving module 901 is further configured to receive a reportmessage sent by the third node, where the report message includesinformation indicating that the first path is marked as a first LSP.

The processing module 902 is further configured to establish a mappingrelationship indicating that the fourth LSP and the first LSP serve asame service, or the receiving module 901 is further configured toreceive a mapping relationship that is sent by the third node and thatindicates that the fourth LSP and the first LSP corresponding to thefirst path serve a same service.

Further, the mapping relationship between the link resource of thefirst-layer network and the link resource of the second-layer network isstored in an LSP database of the second-layer network.

The network path computation apparatus in the foregoing solution may beused to execute the technical solution that is executed by thecorresponding second PCE in the method embodiment shown in FIG. 5A andFIG. 5B, and the implementation principles and technical effects of thetechnical solutions are similar and are not described herein again.

The apparatus in this embodiment adds a resource sharing object to apath computation request sent to a PCE, so as to declare an object thatneeds to be shared; and the PCE computes a path according to theresource sharing object, that is, when computing the path, the PCE mayreuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

FIG. 10 is a schematic structural diagram of an embodiment of a firstnode according to the present invention. The first node may be a headnode of a path, or may be another PCC. As shown in FIG. 10, a first node1000 in this embodiment may include: a transmitter 1001, a processor1002, and a receiver 1003. The figure further shows a memory 1004 and abus 1005. The transmitter 1001, the processor 1002, the receiver 1003,and the memory 1004 are connected and perform mutual communication byusing the bus 1005.

The bus 1005 may be an industry standard architecture (ISA) bus, aperipheral component interconnect (PCI) bus, an extended industrystandard architecture (EISA) bus, or the like. The bus 1005 may becategorized into an address bus, a data bus, a control bus, and thelike. For ease of denotation, the bus is indicated by using only onethick line in FIG. 10, which, however, does not indicate that there isonly one bus or only one type of bus.

The memory 1004 is configured to store executable program code, wherethe program code includes a computer operation instruction. The memory1004 may include a high-speed RAM memory, and may further include anon-volatile memory (non-volatile memory), for example, at least onedisk memory.

The processor 1002 may be a central processing unit CPU), or anapplication-specific integrated circuit (ASIC), or be configured as oneor more integrated circuits that implement this embodiment of thepresent invention.

The transmitter 1001 may be configured to send a path computationrequest to a first path computation element PCE, where the pathcomputation request includes a resource sharing object, and a head nodeand a last node of a first label switched path LSP.

The receiver 1002 may be configured to receive a path computation resultthat is returned by the first PCE and that is obtained by means ofcomputation according to the resource sharing object, and establish asecond path from the head node to the last node according to the pathcomputation result.

Further, the resource sharing object includes an identifier of the firstlabel switched path LSP or an identifier of a normal link in the firstlabel switched path LSP.

Further, the resource sharing object further includes a sharingprinciple.

Further, the sharing principle includes either of the following: sharingas many links as possible is preferred; and a performance parameter isoptimal in a case in which link sharing is ensured, where theperformance parameter includes but is not limited to a delay, jitter, ora hop count.

The first node in this embodiment adds a resource sharing object to apath computation request sent to a PCE, so as to declare an object thatneeds to be shared; and the PCE computes a path according to theresource sharing object, that is, when computing the path, the PCE mayreuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

The apparatus in the foregoing embodiment may be applied to a scenarioin which a first path from a head node to a last node fails. Because asharing policy is used, for example, a path computation request requiresthat a fault-free link in the first path be shared, so that duringcomputation, the PCE can preferentially consider a choice from routesshared with a specified object, and return a computation result; whenthe sharing policy cannot be met, but there is still an availableresource between the head node and the last node (a source node and asink node), return a computation result of non-sharing; and when arequirement for a resource between the source node and the sink nodecannot be met regardless of whether the sharing policy is met, return aresult indicating a path computation failure.

Further, the path computation request may further include an includeroute object IRO. The IRO refers to an object that is “necessarilyincluded”. The solution may be applied to a scenario of switchback to anoriginal link after rerouting. For example, the network path computationapparatus in this embodiment may periodically send a path computationrequest to a PCE, and set the IRO as a link of the first path. In thisway, the PCE can obtain a result indicating a path computation successonly when a fault in the first path is rectified.

Further, the processor 1003 may be configured to determine, before thefirst node sends the path computation request to the path computationelement PCE, that at least one link in a first label switched path LSPbetween a current head node and a current last node fails.

Further, the first node in this embodiment may also be applied to amulti-layer network scenario. A multi-layer network is an application ofa transport network nowadays. Typical scenarios include an IP layer, anoptical layer, and the like. In the multi-layer network scenario, the IPlayer and the optical layer each have a PCE that is responsible for pathcomputation.

When the first node is applied to the multi-layer network scenario,specifically, the head node and the last node belong to a first-layernetwork, the first LSP between the head node and the last node includesat least one link that belongs to a second-layer network, and a headnode of the link of the second-layer network is a third node.

The second path further includes the at least one link in thesecond-layer network.

The processor 1003 is further configured to mark the third path as athird LSP, and the transmitter 1001 is further configured to send, tothe third node, information indicating that the second path is marked asa second LSP, so that the third node sends a report message to a secondPCE in the second-layer network after marking the link of thesecond-layer network as the third LSP, where the report message includesa mapping relationship indicating that the third LSP and the second LSPserve a same service.

In this way, based on the mapping relationship indicating that the thirdLSP and the second LSP serve the same service, in a subsequentcross-layer path computation process, if a specified shared object isthe second LSP, a PCE in a network on another side may determine ashared target in the network at this layer according to the mappingrelationship, so as to support a sharing policy when a cross-layer pathis computed.

The first node in this embodiment may be used to execute the technicalsolution that is executed by the corresponding first node in the methodembodiment shown in FIG. 1, FIG. 4, or FIG. 5A and FIG. 5B, and theimplementation principles and technical effects of the technicalsolutions are similar and are not described herein again.

FIG. 11 is a schematic structural diagram of Embodiment 1 of a PCEaccording to the present invention. The PCE may be a PCE in asingle-layer network, or may be a PCE in a network at a specific layerof a multi-layer network. In a cross-layer path scenario, the PCE is aPCE in a first-layer network (which is referred to as a first PCE), suchas a PCE in an IP layer network. As shown in FIG. 11, a PCE 1100 in thisembodiment may include: a transmitter 1101, a processor 1102, and areceiver 1103. The figure further shows a memory 1104 and a bus 1105.The transmitter 1101, the processor 1102, the receiver 1103, and thememory 1104 are connected and perform mutual communication by using thebus 1105.

The bus 1105 may be an industry standard architecture (ISA) bus, aperipheral component interconnect (PCI) bus, an extended industrystandard architecture (EISA) bus, or the like. The bus 1105 may becategorized into an address bus, a data bus, a control bus, and thelike. For ease of denotation, the bus is indicated by using only onethick line in FIG. 11, which, however, does not indicate that there isonly one bus or only one type of bus.

The memory 1104 is configured to store executable program code, wherethe program code includes a computer operation instruction. The memory1104 may include a high-speed RAM memory, and may further include anon-volatile memory (non-volatile memory), for example, at least onedisk memory.

The processor 1102 may be a central processing unit (CPU), or anapplication-specific integrated circuit (ASIC), or be configured as oneor more integrated circuits that implement this embodiment of thepresent invention.

The receiver 1103 is configured to receive a path computation requestsent by a first node, where the path computation request includes aresource sharing object, and a head node and a last node of a firstlabel switched path LSP.

The processor 1102 is configured to compute a second path from the headnode to the last node according to the resource sharing object.

The transmitter 1101 is configured to send the second path to the firstnode, so that the first node establishes the second path from the headnode to the last node according to the path computation result.

Further, the resource sharing object includes an identifier of the firstlabel switched path LSP or an identifier of a normal link in the firstlabel switched path LSP.

Further, the resource sharing object further includes a sharingprinciple.

Further, the sharing principle includes either of the following: sharingas many links as possible is preferred; and a performance parameter isoptimal in a case in which link sharing is ensured, where theperformance parameter includes but is not limited to a delay, jitter, ora hop count.

Further, the path computation request further includes an include routeobject IRO.

Further, when a technology in the present invention is applied to amulti-layer network (a cross-layer path scenario), the processor 1102may be specifically configured to:

determine that a link resource of a first-layer network in which thefirst node and the second node are located is insufficient to establishthe second path; and

send, to a second PCE in a second-layer network, a request forestablishing a third path, where the request includes the resourcesharing object, the third path is used to form the second path, and thethird path includes at least one link of the second-layer network.

The apparatus in this embodiment may be used to execute the technicalsolution that is executed by the corresponding PCE in the methodembodiment shown in FIG. 1, or the technical solution that is executedby the corresponding first PCE in the method embodiment shown in FIG. 3Aand FIG. 3B, or FIG. 5A and FIG. 5B, and the implementation principlesof the technical solutions are similar and are not described hereinagain.

The apparatus in this embodiment adds a resource sharing object to apath computation request sent to a PCE, so as to declare an object thatneeds to be shared; and the PCE computes a path according to theresource sharing object, that is, when computing the path, the PCE mayreuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

FIG. 12 is a schematic structural diagram of Embodiment 2 of a PCEaccording to the present invention. The PCE may be a PCE in asingle-layer network, or may be a PCE in a network at a specific layerof a multi-layer network. In a cross-layer path scenario, the PCE is aPCE in a second-layer network (which is referred to as a second PCE),such as a PCE in an optical layer network. As shown in FIG. 12, a PCE1200 in this embodiment may include: a transmitter 1201, a processor1202, and a receiver 1203. The figure further shows a memory 1204 and abus 1205. The transmitter 1201, the processor 1202, the receiver 1203,and the memory 1204 are connected and perform mutual communication byusing the bus 1205.

The bus 1205 may be an industry standard architecture (ISA) bus, aperipheral component interconnect (PCI) bus, an extended industrystandard architecture (EISA) bus, or the like. The bus 1205 may becategorized into an address bus, a data bus, a control bus, and thelike. For ease of denotation, the bus is indicated by using only onethick line in FIG. 12, which, however, does not indicate that there isonly one bus or only one type of bus.

The memory 1204 is configured to store executable program code, wherethe program code includes a computer operation instruction. The memory1204 may include a high-speed RAM memory, and may further include anon-volatile memory (non-volatile memory), for example, at least onedisk memory.

The processor 1202 may be a central processing unit (CPU), or anapplication-specific integrated circuit (ASIC), or be configured as oneor more integrated circuits that implement this embodiment of thepresent invention.

The receiver 1203 is configured to receive a request for establishing athird path that is sent by a first PCE in a first-layer network, wherethe request includes a resource sharing object, the third path is usedto form a second path, the third path includes at least one link of asecond-layer network, and the second path further includes at least onelink of the first-layer network.

The processor 1202 is configured to determine a shared target accordingto the resource sharing object and a mapping relationship between a linkresource of the second-layer network and a link resource of thefirst-layer network, and determine the third path according to theshared target.

The PCE in this embodiment may be used to execute the technical solutionthat is executed by the corresponding second PCE in the methodembodiment shown in FIG. 3A and FIG. 3B, and the implementationprinciples and technical effects of the technical solutions are similarand are not described herein again.

Further, in another scenario, for example, when a cross-layer path isestablished for the first time, the receiver 1203 is further configuredto receive, before the second PCE determines the shared target accordingto the resource sharing object and the mapping relationship between thelink resource of the first-layer network and the link resource of thesecond-layer network, a request for establishing a fourth path that issent by the first PCE, where the fourth path is used to form a firstpath, the fourth path includes at least one link of the second-layernetwork, a head node of the second-layer network in the fourth path is athird node, and the first path further includes at least one link of thefirst-layer network.

The processor 1202 is further configured to determine the fourth pathaccording to the request, and return, to the first PCE, a messageindicating that the fourth path is successfully computed.

The processor 1202 is further configured to establish the fourth path,where the fourth path is marked as a fourth LSP.

The receiver 1203 is further configured to receive a report message sentby the third node, where the report message includes informationindicating that the first path is marked as a first LSP.

The processor 1202 is further configured to establish a mappingrelationship indicating that the fourth LSP and the first LSP serve asame service, or the receiver 1203 is further configured to receive amapping relationship that is sent by the third node and that indicatesthat the fourth LSP and the first LSP corresponding to the first pathserve a same service.

Further, the mapping relationship between the link resource of thefirst-layer network and the link resource of the second-layer network isstored in an LSP database of the second-layer network.

The network path computation apparatus in the foregoing solution may beused to execute the technical solution that is executed by thecorresponding second PCE in the method embodiment shown in FIG. 5A andFIG. 5B, and the implementation principles and technical effects of thetechnical solutions are similar and are not described herein again.

The apparatus in this embodiment adds a resource sharing object to apath computation request sent to a PCE, so as to declare an object thatneeds to be shared; and the PCE computes a path according to theresource sharing object, that is, when computing the path, the PCE mayreuse an original link resource or a link resource in a fault-freesection in a faulty path. In this way, link resource utilization can beimproved, and in a scenario of few available link resources in anetwork, a path computation success rate can be improved.

FIG. 13 is a schematic structural diagram of Embodiment 1 of a networkpath computation system according to the present invention. As shown inFIG. 13, a system 1300 in this embodiment may include: a PCC in whichthe network path computation apparatus in the embodiment shown in FIG. 6or FIG. 7 is disposed and a PCE in which the network path computationapparatus in the embodiment shown in FIG. 8 is disposed; or a system1300 in this embodiment may include the first node (that is, a PCC) inthe embodiment shown in FIG. 10 and the PCE in the embodiment shown inFIG. 11.

The network path computation system in this embodiment may be applied topath computation in a single-layer network, or may be applied to pathcomputation in a network at each layer of a multi-layer network. Thesystem in this embodiment may be used to execute the technical solutionof the method embodiment shown in FIG. 1, and the implementationprinciples and technical effects of the technical solutions are similarand are not described herein again.

FIG. 14 is a schematic structural diagram of Embodiment 2 of a networkpath computation system according to the present invention. As shown inFIG. 14, a system 1400 in this embodiment may include: a PCC in whichthe network path computation apparatus in the embodiment shown in FIG. 6or FIG. 7 is disposed, a first PCE that is located in a first-layernetwork and in which the network path computation apparatus in theembodiment shown in FIG. 8 is disposed, and a second PCE that is locatedin a second-layer network and in which the network path computationapparatus in the embodiment shown in FIG. 9 is disposed; or a system1400 in this embodiment may include: the first node (that is, a PCC) inthe embodiment shown in FIG. 10, the PCE (serving as a first PCE) in theembodiment shown in FIG. 11, and the PCE (serving as a second PCE) inthe embodiment shown in FIG. 12.

The network path computation system in this embodiment may be applied topath computation in a multi-layer network, or may be applied tocomputation of a cross-layer path in the multi-layer network. The systemin this embodiment may be used to execute the technical solution of themethod embodiment shown in FIG. 3A and FIG. 3B or FIG. 4, and theimplementation principles and technical effects of the technicalsolutions are similar and are not described herein again.

Persons of ordinary skill in the art may understand that all or some ofthe steps of the method embodiments may be implemented by a programinstructing relevant hardware. The program may be stored in a computerreadable storage medium. When the program runs, the steps of the methodembodiments are performed. The foregoing storage medium includes: anymedium that can store program code, such as a ROM, a RAM, a magneticdisk, or an optical disc.

Finally, it should be noted that the foregoing embodiments are merelyintended for describing the technical solutions of the presentinvention, but not for limiting the present invention. Although thepresent invention is described in detail with reference to the foregoingembodiments, persons of ordinary skill in the art should understand thatthey may still make modifications to the technical solutions describedin the foregoing embodiments or make equivalent replacements to some orall technical features thereof, without departing from the scope of thetechnical solutions of the embodiments of the present invention.

What is claimed is:
 1. A network path computation method comprising:sending, by a first node, a path computation request to a first pathcomputation element (PCE), wherein the path computation requestcomprises a sharing policy specifying sharing the most number of linksfrom a first label switched path (LSP), a head node and a second node,which is a last node, and an identifier of either (a) the first LSP or(b) a normal link in the first LSP; receiving, by the first node, a pathcomputation result returned by the first PCE, wherein the pathcomputation result is obtained according to the sharing policy and theidentifier; and establishing, by the first node, a second LSP from thehead node to the last node according to the path computation result,thereby maintaining the most links from the first LSP in the second LSP,wherein the head node and the last node belong to a first-layer network,the first LSP between the head node and the last node comprises at leastone link that belongs to a second-layer network, a head node of the linkof the second-layer network is a third node, and the second LSP furthercomprises at least one link in the second-layer network; and sending, bythe first node, to the third node, information causing the third node tosend a report message to a second PCE in the second-layer network aftermarking the at least one link in the second-layer network as a thirdLSP, wherein the report message comprises a mapping relationshipindicating that the third LSP and the second LSP serve a common service.2. The method according to claim 1, before sending the path computationrequest to the first PCE, the method further comprising: determining, bythe first node, a failure of at least one link in the first LSP betweena current head node and a current last node.
 3. The method according toclaim 1, wherein the sharing policy and the identifier are carried by aresource sharing object (RSO).
 4. The method according to claim 1,wherein the first LSP and the second LSP have different source nodes anddifferent destination nodes.
 5. The method according to claim 1, whereinthe first LSP and the second LSP have different source nodes ordestination nodes.
 6. A network path computation apparatus comprising: aprocessor; and a non-transitory computer readable medium having aplurality of computer executable instructions that, when executed by theprocessor, cause the processor to perform operations comprising: sendinga path computation request to a first path computation element (PCE),wherein the path computation request comprises a sharing policyspecifying sharing the most number of links from a first label switchedpath (LSP), a head node and a second node, which is a last node, and anidentifier of either (a) the first LSP or (b) a normal link in the firstLSP; receiving a path computation result returned by the first PCE,wherein the path computation result is obtained according to the sharingpolicy and the identifier; establishing a second LSP from the head nodeto the last node according to the path computation result, therebymaintaining the most links from the first LSP in the second LSP, whereinthe head node and the last node belong to a first-layer network, thefirst LSP between the head node and the last node comprises at least onelink that belongs to a second-layer network, a head node of the link ofthe second-layer network is a third node, the second LSP furthercomprises at least one link in the second-layer network; and sending, tothe third node, information causing the third node to send a reportmessage to a second PCE in the second-layer network after marking the atleast one link in the second-layer network as a third LSP, wherein thereport message comprises a mapping relationship indicating that thethird LSP and the second LSP serve a common service.
 7. The apparatusaccording to claim 6, wherein the processor is configured withprocessor-executable instructions to perform operations furthercomprising: determining, before the operation of sending the pathcomputation request to the first PCE, a failure of at least one link inthe first LSP between a current head node and a current last node.
 8. Anetwork path computation method comprising: determining, by a firstnode, a failure of at least one link in a first label switched path(LSP) between a current head node and a current last node, wherein ahead node and a last node belong to a first-layer network; sending, bythe first node, a path computation request to a first path computationelement (PCE), wherein the path computation request comprises a resourcesharing object (RSO) and the head and last nodes, and wherein the RSOcomprises a sharing policy specifying sharing the most number of linksfrom the first LSP and an identifier of either (a) the first LSP or (b)a normal link in the first LSP; receiving, by the first node, a pathcomputation result returned by the first PCE, wherein the pathcomputation result is obtained according to the sharing policy and theidentifier; establishing, by the first node, a second LSP from the headnode to the last node according to the path computation result, therebymaintaining the most links from the first LSP in the second LSP, whereinthe first LSP between the head node and the last node comprises at leastone link belonging to a second-layer network, wherein a head node of theat least one link belonging to the second-layer network is a third node,and wherein the second LSP further comprises at least one link in thesecond-layer network; and sending, by the first node, information to thethird node, causing the third node to send a report message to a secondPCE in the second-layer network after marking the at least one link inthe second-layer network as a third LSP, wherein the report messagecomprises a mapping relationship indicating that the second and thirdLSPs serve a common service.
 9. The method according to claim 8, whereinthe first LSP and the second LSP have different source nodes anddifferent destination nodes.
 10. The method according to claim 8,wherein the first LSP and the second LSP have different source nodes ordestination nodes.
 11. A system comprising a first node and a first pathcomputation element (PCE), wherein the first node is configured to senda path computation request to the first PCE, wherein the pathcomputation request comprises a sharing policy specifying sharing themost number of links from a first label switched path (LSP), a head nodeand a second node, which is a last node, and an identifier of either (a)the first LSP or (b) a normal link in the first LSP; the first PCE isconfigured to determine a second LSP from the head node to the last nodeaccording to the sharing policy and the identifier and send the secondLSP to the first node; the first node is further configured to establisha second LSP from the head node to the last node according to the pathcomputation result, thereby maintaining the most links from the firstLSP in the second LSP, wherein the head node and the last node belong toa first-layer network, the first LSP between the head node and the lastnode comprises at least one link that belongs to a second-layer network,a head node of the link of the second-layer network is a third node, andthe second LSP further comprises at least one link in the second-layernetwork; and the first node is further configured to send, to the thirdnode, information causing the third node to send a report message to asecond PCE in the second-layer network after marking the at least onelink in the second-layer network as a third LSP, wherein the reportmessage comprises a mapping relationship indicating that the third LSPand the second LSP serve a common service.
 12. The system according toclaim 11, wherein before sending the path computation request to thefirst PCE, the first node is further configured to determine a failureof at least one link in the first LSP between a current head node and acurrent last node.
 13. The system according to claim 11, wherein thesharing policy and the identifier are carried by a resource sharingobject (RSO).
 14. The system according to claim 11, wherein the firstLSP and the second LSP have different source nodes and differentdestination nodes.
 15. The system according to claim 11, wherein thefirst LSP and the second LSP have different source nodes or destinationnodes.